Lithological-paleontological characteristics of the Jurassic and Cretacyte deposits of the fields of the Middle Obi

Abstract

The oil and gas potential of Western Siberia, for the most part, is associated with Jurassic and Cretaceous deposits. For many years, the main oil production has been in the Middle Ob region. The conditions and factors contributing to the formation of productive formations, the study of which does not lose its relevance today, are of particular importance for the distribution of hydrocarbons in the reservoir. In the work, according to the study of core material, the lithological and paleontological characteristics of three main formations of Cretaceous and Jurassic deposits of fields in the central part of Western Siberia of the Surgut and Nizhnevartovsk vaults are given. According to the core study data, the main lithotypes of sediments were identified according to the totality of features within the study area with the characteristic of the biogenic component of the section. An ichnofacial analysis of the traces of the life activity of ground species isolated from the data of the well core study was carried out. The facies belonging of the deposits was established by a comprehensive analysis of textural features, structural features, as well as the study of traces of the organic component. A comprehensive study of the sedimentological and paleontological components of productive sediments allowed us to establish sedimentation conditions: the formation of sediments occurred in two dynamic environments – littoral and sublittoral zones. Keywords: drill sample; facies; ichnofacies; bioturbation; depositional environment; ichnofossil; Jurassic sediments; Cretaceous deposits.